WO2013107969A1

WO2013107969A1 - Apparatus using electromagnetic waves to detect the motion of a masked body

Info

Publication number: WO2013107969A1
Application number: PCT/FR2013/050074
Authority: WO
Inventors: Florent Christophe; François Issac
Original assignee: ONERA (Office National d'Etudes et de Recherches Aérospatiales)
Priority date: 2012-01-19
Filing date: 2013-01-11
Publication date: 2013-07-25
Also published as: EP2805184B1; FR2986077B1; FR2986077A1; EP2805184A1

Abstract

An apparatus for detecting the motion of a masked body which is present in a load (100) combines an emission-reception of radiation through the load, and the production of a Faraday cage (1) around the load. The apparatus exhibits a sensitivity which is compatible with detection of the presence of live beings, without an operator entering the load or a probe being introduced thereinto.

Description

ELECTROMAGNETIC WAVE DETECTION APPARATUS FOR MOVING A MASK BODY

The present invention relates to an apparatus and method for electromagnetic wave detecting movement of a masked body in view within a load.

Some situations need to control that a load does not contain living beings, human or animal. This may be the case for border controls, for example, to search for stowaways in vehicles or to combat trade in protected live animal species. Some methods that are used for such controls include manual search, the use of screening dogs, the use of acoustic sensors, x-ray radiography, or the analysis of fumes gas from the load. But these methods have the following disadvantages, which vary according to the method used and the circumstances in which the control is carried out:

- the duration of the control can be long, and incompatible with a flow of loads passing through the control point;

- a cost of the means that are implemented, or an operating cost of the control itself, can be high;

the detection may be unreliable or based on the interpretation of images by an operator, or have a false alarm rate which is high;

- the control can be dangerous for an operator of its implementation, or for the sought-after persons, in particular when ionizing radiations are used; and

- the execution of the control may require access to the interior of the load, for an operator or a detection probe that must be placed there.

In particular, many circumstances can prevent access to the interior of the load, for an operator or a detection probe: either for lack of time, or because the load is contained in an airtight enclosure, or because of risks related to the unknown nature of the load, because of seals that have been affixed to the load, or for other reasons. It is then necessary that the control means which are used be non-intrusive, that is to say that the detection can be carried out remotely through an envelope, walls or a vessel which encloses the load. In addition, the detection method that is implemented must have sufficient detection sensitivity to provide a high level of control reliability.

The document which is titled "A Study of UWB FM-CW Radar for the Detection of Human Beings in Motion Inside a Building", by N. Maaref et al., IEEE Transactions on Geoscience and Remote Sensing, Vol. 47, No. 5, May 2009, proposes a detection method that is based on the disturbance of the electromagnetic diffraction properties caused by the presence of a living being moving behind a wall. The sensitivity that is obtained can reveal a person who moves in a building, and could even be sufficient if the wall is not very absorbent and if there are no other obstacles interposed to detect movements of being alive which have much weaker amplitudes, such as breathing movements, heart beats, etc.

Document US Pat. No. 6,031,482 proposes a radar system for detecting and locating an individual by virtue of his or her only respiratory movements, for example for a victim who is buried by an avalanche of snow. However, the detection sensitivity is not sufficient to be applied to certain loadings, especially when the content of the load is unknown and heterogeneous or that its envelope is partially metallic.

Under these conditions, an object of the present invention is to provide a new motion detection means inside a load, which does not have the disadvantages of known systems or for which these disadvantages are reduced.

In particular, a first object of the invention is to provide a means of detection that is compatible with variable load configurations and sizes. In particular, the detection means is sought to be effective when a charge is contained in a metal casing that has openings that are small or restricted for penetration by electromagnetic radiation.

A second object of the invention is to provide a detection means which does not depend on the interpretation capabilities of an operator, and does not present a danger for an operator in charge of supervising the detection.

A third object of the invention is to detect a body movement inside a load with high detection reliability, especially with respect to parasitic sources of motion or radiation that may be present at the same time. outside of the load.

To achieve these and other objects, the invention provides an apparatus for electromagnetic wave detection, movement of a body which is masked in view in a load at least partially transparent to electromagnetic waves. The detection apparatus comprises:

an enclosure device, which is adapted to contain the load and to form a Faraday cage around the load;

a radiofrequency transceiver system, which is adapted to produce primary electromagnetic radiation within the Faraday cage and the charging, and for detecting at least one secondary electromagnetic radiation generated from the primary radiation by a motion occurring in the shipment; and

a spectral analysis system, which is connected at the input to a detection output of the transceiver system, and which is adapted to produce an alarm signal when the secondary radiation has spectral characteristics which are included in a memorized detection target. The frequency of the primary radiation is adapted so that the Faraday cage and the loading have dimensions able to reverberate the primary and secondary radiations. In addition, the spectral analysis system is adapted to analyze the secondary radiation in two spectral intervals which are each between 0.1 Hz and 100 Hz from the frequency of the primary radiation on each side thereof.

Thus, according to the invention, the load to be controlled is enclosed within an enclosure acting Faraday cage during the control. Such a configuration constitutes at least partial electromagnetic insulation between the inside and the outside of the enclosure, from which the following advantages result:

- the electromagnetic radiation that is used for the detection is produced inside the enclosure and remains confined within it, so that the constraints of the radio regulations are reduced, and a control operator who is located outside the enclosure is not exposed to radiation;

- The useful radiation, primary and secondary, which are confined in the enclosure are less sensitive to sources of movement, vibration, or parasitic radiation that may be present outside the enclosure; and

the confinement of the radiation reduces the radiative losses in the environment, so that a power supply which is reduced is sufficient to produce a radiation intensity fixed in the chamber, and adapted with respect to the sensitivity of the detection.

The enclosure is reverberant for the confined radiation, so that the primary and secondary radiation are reflected in all directions within the enclosure. In this way, the radiation can enter and leave parts of the load, even if they are located in shadows with respect to direct exposure to the transceiver system. For example, the load can be protected by a metal envelope that has only a reduced opening, or the The body may itself be contained in a metal container which has only a small opening. It is then exposed to a part of the primary radiation, thanks to the isotropy or quasi-isotropy of the circulation of radiation in the enclosure. For the same reason, the secondary radiation that is generated by the movement of the body inside the container or envelope, diffuses out of the container or envelope by its opening and then reaches the receiving system after multiple reflections on the walls of the enclosure, inside it.

In a known manner, as explained for example in the reference available via the Internet at

http://www.ieee.org/organizations/pubs/newsletters/emcs/fall99/reverb.htm, an enclosure is reverberant for radiation when this radiation is propagated by successive reflections on the walls of the enclosure, at the inside of it. The radiation is then distributed quasi-isotropically throughout the internal volume of the chamber and passes at each point of this volume in a multiplicity of propagation directions. For this, the enclosure preferably has internal dimensions which are much greater than the wavelength of the radiation, for example in a ratio of one or more tens. The isotropy of the radiation distribution in the internal volume of the chamber can be improved by changing the frequency of this radiation, so as to eliminate areas of residual shadows.

In the context of the present invention, the primary radiation is that produced by the emission system inside the enclosure, directly or after having undergone reflections inside the reverberant enclosure. The secondary radiation results from the interaction between the primary radiation and the mobile part which is possibly present inside the enclosure. Its intensity can be very low. Pragmatically, it can be assumed that the secondary radiation has a frequency deviation with the primary radiation which is included in the spectral analysis range of the detection systems used.

In the context of the present invention, we finally call the target of detecting a set of predetermined spectral characteristics which are examined for secondary radiation, and which correspond to a type sought for the motion source. In general, the detection target corresponds to movements that would be generated by moving parts of the body.

The body that is possibly present in the loading is detected by modifications of some of the spectral characteristics of the secondary radiation, which are caused by movements of the body itself. In particular, the movement of the body can produce the secondary radiation by Doppler effect from the primary radiation, it being understood that such a Doppler effect appears regardless of the wave structure of the primary radiation at the location of the body. In particular, because of the reverberation in the chamber, the primary radiation has components that propagate in several different directions at the body. These radiation components can then each be differently affected by the movement of the body, in particular as a function of the configuration of the mobile part of the body, and the relative orientations of the movement of this moving part and the direction of propagation of each radiation component. . In general, the spectral signature of the movement of the body in the radiation that is detected is complex, but it exhibits features indicative of movement. These revealing characteristics concern in particular the frequency difference and / or the intensity ratio between the primary and secondary radiations. In general, body movements that can be detected with the apparatus of the invention can have velocities or amplitudes that produce very low Doppler effects, usually referred to as micro-Doppler.

Thanks to the use of radiofrequency radiation, the apparatus allows a very effective control of the content of the load, relative to the presence of moving parts, and particularly with respect to body movements of living beings that would be hidden in the load. Indeed, all materials that are electrically insulating and those with low electrical conduction, are transparent or partially transparent for radiofrequency radiation. Moreover, thanks to the reverberant configuration of the enclosure, a metal element that is not transparent by itself for the radiation does not cause or little shadow area due to the multiplicity of directions of propagation of radiation in the enclosure. Only moving parts that would be contained in completely closed metal containers or envelopes can not be detected using the apparatus of the invention. In order for the apparatus to nevertheless perform an effective detection in the presence of such metal containers or shells, it suffices that they are at least partially open before the detection sequence is applied to the loading. To provide maximum detection sensitivity with respect to movements that occur in the load, the apparatus may further have some of the following additional features, taken alone or in combination of several of them:

the primary radiation may have a frequency which is between 100 MHz (megahertz) and 100 GHz (gigahertz), preferably between 500 MHz and 5000 MHz;

the radiofrequency transmission-reception system may be of the heterodyne type;

the detection target may correspond to proprioceptive, respiratory or cardiac movements of a living being, possibly asleep or seeking to remain motionless, which constitutes the body;

the primary radiation may have several components with respective frequencies which are different, in particular so as to reduce the residual shadows; and

the radiofrequency transmission-reception system can be adapted to vary the frequency of the primary radiation according to a sequence of determined values, with a reception latency delay between two frequency values which are successively controlled. In addition, the speaker device that forms the Faraday cage may have several configurations, adapted to types of loadings variables or different control circumstances. Among these configurations, the following are preferred:

the enclosure device may comprise at least one door that participates in the Faraday cage when the door is closed; the enclosure device may comprise a closed parking space for a vehicle, with at least one entrance door for the vehicle, walls, a ceiling and a floor all of which are electrically conductive;

- The enclosure device may comprise a tent whose surfaces are electrically conductive, the tent being open in a lower section, and adapted to be brought from above the load and placed around it on a portion of ground made conductive electrically. For example, the soil portion may be made conductive by the prior placement of a metallized carpet, or a liquid that is electrically conductive may be spread beforehand on the ground portion, or injected therein. In this way, the soil portion can have a level of electrical conduction that is sufficient to form the Faraday cage with the tent. Optionally, the tent may be adapted to be deployed from a folded configuration, and then folded back after use; and

- Finally, the detection apparatus may further comprise a conveyor system, which is adapted to introduce the load into the enclosure device.

The invention also provides a method for detecting by electromagnetic wave, movement of a body which is masked in view in a load at least partially transparent to electromagnetic waves. The method comprises the following steps:

IM determining a detection target for spectral characteristics, corresponding to motions that would be generated by moving parts of a body;

121 form a Faraday cage around the load; 13 / within the Faraday cage, producing primary electromagnetic radiation which has at least one frequency adapted for this radiation to reverberate inside the Faraday cage and the loading, and activate a detection system of secondary electromagnetic radiation in two spectral ranges which are each between 0.1 Hz and 100 Hz from the frequency of the primary radiation on each side thereof;

Spectrally analyzing the detected secondary radiation to produce spectral characteristics thereof; and generating an alarm signal when the spectral characteristics of the secondary radiation are included in the detection target.

Such a detection method can be implemented using a detection apparatus according to the invention, as described above.

The body can belong to a living being that is located inside the load, so that the detection process can be applied in search of being alive, human or animal, in the load.

Finally, in improvements of the invention, the detection method may further comprise an additional learning step to avoid false alarms which may be caused by parasitic movements which are external to the body and which produce characteristics. spectrum for the secondary radiation included in the detection target. Such learning can also avoid false alarms that may be caused by uninteresting movements in relation to a predefined search goal for the body. Other features and advantages of the present invention will become apparent in the following description of nonlimiting exemplary embodiments, with reference to the appended drawings, in which:

FIGS. 1a to 1c respectively illustrate three configurations of detection devices according to the invention; FIG. 2 is a block diagram of a transmission-reception and analysis system, possible for a detection apparatus according to the invention; FIG. 3 illustrates a spectral distribution of radiation detected during use of an apparatus according to the invention; and

FIGS. 4a and 4b respectively illustrate two radiofrequency transmission sequences that can be used in a detection apparatus according to the invention.

For the sake of clarity, the dimensions of the elements which are represented in these figures do not correspond to real dimensions nor to actual dimension ratios. In addition, identical references which are indicated in different figures designate identical elements or which have identical functions. Finally, in FIGS. 3, 4a and 4b, the notations adopted are the following: t denotes the time during an operating sequence of the apparatus, f is a radiation frequency produced or detected, and Δί is a difference between the frequency radiation produced and that of a detected radiation. According to FIGS. 1a to 1c, a detection apparatus according to the invention is used in a load control station. The apparatus comprises an enclosure 1 which is adapted to contain the load 100, possibly with objects and ancillary equipment, such as a load container, a trailer, a transport truck, a conveyor system, etc. One of the advantages of the invention lies in that it makes it possible to control the load 100 without unloading it or separating it from its transport or conveying equipment, so that no manipulation of the load 100 is necessary. In this way, the control can be fast, in particular to be performed on a large number of successive loads. The enclosure 1 forms a Faraday cage around the load 100.

For this, the chamber 1 has side walls, a ceiling and a floor which are electrically conductive, so as to reflect electromagnetic radiation inside the chamber 1. In addition, these surfaces of the enclosure 1 are adapted to be as impermeable as possible with respect to radiation leakage from the inside of the enclosure 1 to the outside. Similarly, the enclosure 1 prevents as much as possible external electromagnetic radiation that has wavelengths in the interval used spectral can not penetrate the enclosure. The skilled person knows how to make such Faraday cages, by using continuous metallic or metallized surfaces which are electrically joined together, or metal trellises with sufficiently fine mesh. In particular, the floor may contain a wire mesh which is embedded in a cement screed. The enclosure 1 is therefore characterized by its screen function against the transmission of electromagnetic radiation, both from the inside to the outside and from the outside to the inside, but it can have very different embodiments. varied. Figure 1a shows an enclosure 1 which constitutes a parking shed, capable of enclosing a vehicle of road transport of very large size. Advantageously this shed can be designed to facilitate the entry and exit of the vehicle to reduce the duration of the control. For this, it can have the form of a tunnel through, being equipped with an entry door 2 and an exit door 3 for the vehicle, which are located at opposite ends of the shed to reduce to a maximum the maneuvers of the vehicle. A person evacuation door 4 may also be added, to allow the driver of the vehicle to quickly exit the enclosure 1 after stopping the vehicle. The door 4 can indeed be closed more quickly than the doors 2 and 3 whose larger dimensions require more substantial actuating means, and often slower. Obviously, all the doors 2 to 4 must also be reflective for the electromagnetic radiation that is used for the control, and equipped with appropriate peripheral seals to ensure continuity of electrical conduction between these doors and the fixed walls of the enclosure 1.

FIG. 1b shows an alternative embodiment of the enclosure 1, which is adapted to control a container 100. In this case, the enclosure 1 can be traversed by a roller conveyor 102, with a stop station of each container 100 in a position where the enclosure 1 can be completely closed around the container. A module of the conveyor 102 may be entirely contained in the enclosure 1, if the floor of the enclosure 1 below this conveyor module is electrically conductive to close the Faraday cage from below. Finally, Figure 1c shows a control station according to the invention, which can be quickly transported and installed at the location of a load 100 to control, such as an abandoned trailer. In this case, the enclosure 1 can be made in the form of a flexible and foldable tent, mesh or conductive fabric. To produce the Faraday cage function, the ground must be sufficiently electrically conductive below the load 100, and a conductive mat could be unwound or deployed for this purpose. Optionally, an ionic liquid 101, especially a saline solution, may be spread on the ground or injected into the ground under the charge 100, to make it electrically conductive without moving the charge 100. Electromagnetic screen continuity must still be ensured between the unfolded tent and the ground made conductive, for example by pressing the lower peripheral edge of the tent on the ground.

The detection apparatus further comprises a radiofrequency transmission-reception system 7 and a spectral analysis system 8 (FIG. 2). The radiofrequency transceiver system 7 itself comprises a transmitting antenna 5 and a detection antenna 6 which are situated inside the enclosure 1. The spectral analysis system 8 can be combined with a radiofrequency radiation source 10, in one of the ways known to those skilled in the art, for example to perform a heterodyne detection of the radiation which is perceived by the detection antenna 6 Such a combination can also facilitate synchronization between transmission and detection sequences of radio frequency radiation.

Antennas 5 and 6 may possibly be confused, the skilled person being able to add a device for separating the incoming and outgoing waves of a single antenna.

Thanks to its Faraday cage function, the chamber 1 reverberates within itself the primary electromagnetic radiation that is produced by the transmitting antenna 5, as well as the secondary electromagnetic radiation that is perceived by the In general, the internal dimensions of the chamber 1 are at least ten times larger than the wavelengths of the primary and secondary radiations. For example, the smallest inner dimension of the enclosure 1 may be a few meters, while the primary radiation that is used may have a frequency of the order of 1000 MHz, which corresponds to a wavelength close to 30 cm. The frequency (s) of the secondary radiation has (have) value (s) which is (are) very close to that of the primary radiation, because the secondary radiation is generated by moving parts that are slow relative to the primary radiation. Under these conditions, the primary and secondary radiation propagate similarly throughout the interior of the chamber 1.

The transmitting antenna 5 can produce the primary radiation with a power of 10 mW (milliwatt) for example. Such a power level makes it possible to obtain a good detection sensitivity, without, however, exposing an individual who would possibly be present inside the charge 100 at an electromagnetic field level higher than the authorized limits.

The load 100 may itself contain electromagnetic radiation impermeable volumes, such as metal containers, or have configurations that form protected areas with respect to radiation penetration. In these cases, the control of the load 100 with respect to the presence of movements is effective for the entire volume of the load with the exception of the impervious volumes or protected areas. Advantageously, metal containers which are identified inside the load 100 may be opened during the inspection, in order to expose their internal volume to the radiation. It is stated in this connection that standardized containers have wooden floors, so that radiation can enter the container and emerge from its underside.

According to a first possible architecture for the radiofrequency transmission-reception system, it may be of the heterodyne type to provide a detection sensitivity that is compatible with the search for movements that would occur in the load 100.

According to an alternative possibility illustrated in FIG. 2, the transmission-reception system 7 comprises the radiofrequency signal source 10 which feeds the transmitting antenna 5 to produce the primary radiation. Furthermore, an output of the detection antenna 6 is connected to the spectral analysis system 8 which comprises in the order: a first amplifier 1 1, a mixer 12, a second amplifier 13, an analog filter 14, a converter analog-digital 15 noted CAN, a digital filter 16, a threshold comparator 17 and a visual alarm device (FIGS. 1a-1c) or audible alarm (FIG. 2) referenced 18. The connections of the antennas 5 and 6 respectively with the source 10 and the amplifier 1 1 may be constituted by coaxial cables for radiofrequency transmission. The operating principle of such a detection and analysis chain is known. The mixer 12 simultaneously receives the amplified detection signal on a first input, and a reference signal which is produced by a local oscillator denoted OL and referenced 20. For this, a synchronization unit 21, denoted SYNCHRO, controls both the source 10 and local oscillator 20 for coordinating primary radiation emission and secondary radiation detection sequences. The template of the filter 16 and the threshold of the comparator 17 which are made numerically correspond to the detection target. For example, the detection target may contain a first condition according to which the frequency of one of the components which is isolated by the filter 16 and transmitted by the comparator 17 has a frequency deviation with the primary radiation greater than a spectral width of the signal source of the source 10. This spectral width can be, for example,

0.5 Hz. A second condition of the detection target may be an upper limit value for the same frequency deviation, for example an upper limit value of 5 Hz, in order to suppress parasitic contributions to the signal that is transmitted by the system. 8. Such parasitic contributions can be due to movements occurring inside the enclosure 1, which are too fast to be attributed to moving parts of living beings. They can also be due to parasitic electromagnetic radiation coming from external devices to the enclosure

1, for which the screening by the Faraday cage is not completely effective. Finally, parasitic movements can also be detected, which have origins external to the loading 100 but which are transmitted to charging or to the enclosure 1, for example in the form of resonances or mechanical vibrations. This may be the case for drops of rain falling on the roof of the enclosure 1, gusts of wind that make it vibrate, air currents that seep inside the enclosure 1 by interstices thereof or vibrations that are transmitted by the ground. However, to reduce the detected parasitic components that would be due to such external sources, the enclosure 1 may be provided with a waterproof double-roof. Similarly, the vehicle and / or the load 100 may be dried prior to the check if they have been exposed to a heavy rain that would cause runoff to occur. inside the enclosure 1 during the check. For a control device which is in accordance with FIG. 1b, the conveyor modules 102 which are located near the enclosure 1 are preferably stopped during the control, to also avoid the vibrations that these modules can generate and which may be transmitted through the ground to the inside of the enclosure 1.

To possess sufficient frequency stability, the local oscillator 20 can be selected to detect even slow movements that would occur within the load 100.

In an alternative configuration, the filter 16 may be replaced by a battery of parallel filters to perform a spectral analysis, which may in particular be performed by Fast Fourier Transform, known by the acronym FFT for Fast Fourier Transform in English, so as to better to differentiate the effects produced by the movements of a body and the effects of parasites. FIG. 3 schematically shows a spectral analysis result of the secondary radiation which can then be obtained by the system 8. The identification of spectral components in the secondary radiation can be limited to an interval which extends for example to 5 Hz on both sides of the primary radiation. This primary radiation is taken as origin in the diagram of FIG. 3. The spectral analyzer 16 is preferably adapted to provide a resolution which is less than or equal to 0.5 Hz, for example equal to 0.1 Hz, for frequency of each spectral component of the secondary radiation that is identified. For example, the spectral resolution with which the secondary radiation is analyzed can be 10 to 100 times smaller than the width of the spectral analysis interval around the frequency of the primary radiation. The spectral analysis which is thus carried out can make it possible to retain only the spectral components which exceed the threshold denoted Lin for distinguishing a detection signal which is significant with respect to a measurement noise or a limit of sensitivity of detection. Pattern recognition methods known to those skilled in the art can also be used to compare the spectrum that is obtained by the analyzer 16 to spectra recorded in a prior learning phase, so as to reduce false alarms and / or or specify characteristics of the detected living being.

Preferably, to reduce possible shadow areas in the charge and increase the sensitivity of the motion detection, the primary radiation that is generated by the source 10 may comprise several subcarriers that have different respective frequencies, for example four subcarriers of frequency fi to f ₄ . By way of illustration, the frequency f 1 can be of the order of 1000 MHz, and the frequencies h to f ₄ are obtained from the frequency f by applying successive increments of 25 MHz. According to a first possible transmission-detection sequence, and illustrated in FIG. 4a, the four sub-carriers of the primary radiation can be produced continuously and simultaneously for a duration which can be of the order of 10 s (second), by example. Detection of the secondary radiation can then also be carried out continuously during this time by four identical channels to that described above, and each adapted to one of the four frequencies. According to a second transmission-detection sequence which is equivalent but more economical to produce, and illustrated in FIG. 4b, the different subcarriers of the primary radiation can be produced successively by time multiplexing, in separate time intervals of time. At _least one of the subcarriers is reconstituted by demultiplexing at the output of the converter a single reception channel which is preferably activated with a latency time after each start of transmission of the primary radiation with a new frequency. so that a radiation remanence or a transient regime due to the reverberation by the enclosure 1 has disappeared. Thus, the detection _of At reception time for each sub-carrier of the primary radiation in the sequence of Figure 4b is shorter than the duration At _S0U rce- For example, At and At _S0U rce _of detection may be respectively equal to 100 s (microsecond) and 80 s, with the succession of frequency values of primary radiation that is repeated periodically.

The output energy of the digital filter 16 can be cumulated for the different subcarriers before transmission to the comparator 17, but it is also possible to further reduce the sensitivity to noise according to the method known under the designation "p among n ", first compare the energy output of the filter 16 to a threshold for each of the subcarriers and then decide on a detection if p at least n subcarriers have led to exceeding the threshold, p and n being non-zero natural whole numbers.

Thus, the detection apparatus which constitutes the loading control station has characteristics of emission stability and detection sensitivity which make it possible to identify contributions to secondary radiation due to a living being that would be hidden at the same time. 100. This living being, whether human or animal, is detected by the voluntary, reflex or vital movements it produces, such as its heartbeat, breathing, or reflexes to maintain body position. These movements produce from the primary radiation that is emitted in the chamber 1, one or more spectral component (s) of secondary radiation which is (are) detected (s). The physical mechanism (s) by which the secondary radiation components are produced is of little importance as to their exact physical nature. However, the Doppler effect has been identified by the inventors as one of the preponderant physical mechanisms, while being of very low amplitude. Because of this very small amplitude, it is preferable that any cause of motion that is already known be removed. In particular, in the case of the control station of Figure 1a, the engine and the air conditioning of the vehicle are cut and the driver is out of the chamber 1 by the door 4 by closing the latter. However, some sources of parasitic components that are present in the secondary radiation can not be extinguished. In this case, these parasitic components can be characterized during a learning step of the analysis system 8, and then discarded when the load 100 is controlled. For example, a motion detection sequence can be performed when the enclosure 1 is empty, that is to say without the load 100. The detection and analysis method which has just been described then characterizes contributions secondary radiation, regardless of the mechanical or electromagnetic origin of these contributions. When the detection and analysis method is then repeated with the charge 100 introduced into the chamber 1, the parasitic contributions which have previously been identified with the empty chamber 1 can be eliminated from the analysis of the detection signal. The secondary radiation components which are indicated in broken lines in FIG. 3 and referenced PP, for parasitic peak, and which can be produced for example by a mechanical vibratory mode of the 4 Hz enclosure, are such an original contribution. external to the loading 100, and are eliminated by the spectral analysis of the load control 100.

Obviously, the detection apparatus of the invention can be used in the same way to search for the presence of any movement that would occur inside the load 100, whatever its origin and especially even if this movement is caused by a device instead of a living being.

At the end of the check, the driver of the vehicle carrying the load 100 (FIG. 1 a) can enter the enclosure 1 again through the door 4. The two doors 2 and 3 are simultaneously open, so that the vehicle of the loading 100 which has just been checked out at the same time as the vehicle of the next load to be checked enters the enclosure 1.

Finally, the most significant advantages of a detection apparatus that is in accordance with the invention are now recalled: the device makes it possible to search for and detect a movement that occurs in a load, without an operator entering the loading. A number of operators for cargo control can then be reduced, and no operator is exposed to the risks associated with entering an unknown load or its manual search;

- no operator is required to image analysis that requires frequent rest to address the risk of a decline in attention;

- The control time of a load is short, and the result of the check is available immediately. Controls can thus be chained one after the other when pending loads are introduced successively inside the enclosure; the Faraday cage that is implemented reduces parasitic components that may be present in the detection signal;

- It is not necessary to unload the load of a vehicle or a transport trailer, or a conveyor, to implement the detection method of the invention; and

- a control operator is not exposed to the radiation used, since this radiation remains confined inside the Faraday cage, and the operator remains outside of it.

Claims

1. Apparatus for detecting by electromagnetic wave, movement of a body masked in view in a load (100) at least partially transparent to electromagnetic waves, said apparatus comprising: - an enclosure device (1) adapted to contain the charge and to form a Faraday cage around said load;

a radiofrequency transmission-reception system (7) adapted to produce primary electromagnetic radiation inside the Faraday cage and the charging, and for detecting at least one secondary electromagnetic radiation generated from the primary radiation by a motion occurring in the shipment; and

a spectral analysis system (8), input connected to a detection output of the transmission-reception system, and adapted to produce an alarm signal when the secondary radiation has spectral characteristics which are included in a target in which at least one frequency of the primary radiation is adapted so that the Faraday cage and the load have dimensions capable of reverberating said primary and secondary radiations, the spectral analysis system is adapted to analyze the secondary radiation in two spectral intervals each between 0.1 Hz and 100 Hz from the primary radiation frequency, on each side of said primary radiation frequency; and the detection target corresponds to movements generated by moving parts of a body.

2. Detection apparatus according to claim 1, wherein the primary radiation has a frequency between 100 MHz and 100 GHz.

3. Detection apparatus according to claim 1 or 2, wherein the radiofrequency transmission-reception system (7) is heterodyne type.

4. Detection apparatus according to any one of the preceding claims, wherein the detection target corresponds to proprioceptive, respiratory or cardiac movements of a living being constituting said body.

5. Detection apparatus according to any one of the preceding claims, wherein the primary radiation has several components with different respective frequencies.

6. Detection apparatus according to any one of the preceding claims, wherein the radiofrequency transmission-reception system (7) is adapted to vary said at least one frequency of the primary radiation according to a sequence of determined values, with a delay of reception latency between two frequency values controlled successively.

7. Detection apparatus according to any one of the preceding claims, wherein the enclosure device (1) comprises at least one door (2-4) participating in the Faraday cage when the door is closed.

8. Detection apparatus according to any one of claims 1 to 7, wherein the enclosure device (1) comprises a closed vehicle parking enclosure, with at least one entrance door for said vehicle, walls, electrically conductive ceiling and floor.

9. Detection apparatus according to any one of claims 1 to 7, wherein the enclosure device (1) comprises a tent electrically conductive surfaces, said tent being open in a lower section, and adapted to be brought by the above the load and placed around said load on a portion of soil (101) electrically conductive.

The detection apparatus of claim 9, wherein the tent is adapted to be deployed from a folded configuration, and then folded back after use.

1 1. Detection apparatus according to any one of claims 1 to 7, further comprising a conveyor system (102) adapted to introduce the load (100) into the enclosure device (1).

12. A method for detecting by electromagnetic wave, movement of a masked body in a view (100) at least partially transparent to electromagnetic waves, comprising the steps of: IM determining a detection target for spectral characteristics, corresponding to movements generated by moving parts of a body;

121 form a Faraday cage around the load;

13 / within the Faraday cage, producing primary electromagnetic radiation having at least one frequency adapted for the radiation to reverberate within the Faraday cage and the charging, and activate a radiation detection system secondary electromagnetic radiation in two spectral ranges each between 0.1 Hz and 100 Hz from the primary radiation frequency, on each side of said primary radiation frequency;

Spectrally analyzing the detected secondary radiation to obtain the spectral characteristics of said secondary radiation; and generating an alarm signal when the spectral characteristics of the secondary radiation are included in the detection target.

13. The detection method according to claim 12, implemented using a detection apparatus according to any one of claims 1 to 1 1.

14. The detection method according to claim 12 or 13, wherein the body belongs to a living being located inside the load (100).

The detection method according to any one of claims 12 to 14, further comprising an additional learning step to avoid false alarms caused by parasitic movements which are external to the body and which produce spectral characteristics for the radiation secondary to the detection target, or to avoid false alarms caused by movements of no interest compared to a predefined search objective for the body.

The method of claim 13, wherein the sensing apparatus is in accordance with claim 9 and an electrically conductive liquid (101) is previously spread over the ground portion or injected into said ground portion.